Question

A boy weighing 50 kgf climbs up from the first floor at a height of 3 m above the ground to the third floor at a height of 9 m above the ground. What will be the increase in his gravitational potential energy? (Take g = 10 N kg^-1).

Answer 1

Force acting on body = 50 kgf

= [50 kg × 10] N

= 500 N

As height change from 3 m to 9 m

∴ Increase in energy in, rising from 3 m to 9 m above the ground = mgh₂ – mgh₁

= mg [h₂ – h₁]

= 500 [9 – 3]

= 500 × 6

= 3000 J